Feasibility of Assessing Bone Mineral Density Based on Hydroxyapatite-(iodine) Image Analysis in Contrast-Enhanced Dual-Energy Spectral CT Imaging

Abstract Background. To explore the feasibility of using hydroxyapatite (HAP) measurement based on the material decomposition in dual-energy spectral CT imaging to evaluate bone mineral density (BMD).Methods. 247 patients (aged 16 to 97 years, 156 males and 91 females) who underwent both unenhanced and contrast-enhanced (arterial-, venous- and delayed-) phase abdominal dual-energy spectral CT were retrospectively collected. Patients were divided into four groups according to their ages: group A (<30years, n=40), group B (30-49years, n=90), group C (50-69years, n=73) and group D (≥70years, n=44). HAP densities of trabecular bone of the third lumbar vertebrae in four phases were measured on the HAP material decomposition images using HAP-Iodine as the basis material pair and recorded. HAP as function of age was established and measurements in four phases were statistically compared using that in unenhanced phase as the reference standard.Results. No statistical difference was found in HAP value among different imaging phases (P>0.05). The HAP value was positively correlated with age in group A (r=0.393, P<0.05) and negatively correlated with age in groups B, C and D (r=-0.298, -0.361, -0.361, P<0.05), and overall high negative correlation with age for patients ≥30years (r=-0.775, P<0.05).Conclusions. The HAP measurement is not affected by contrast agent and stable in different imaging phases in dual-energy spectral CT, enabling a phase-independent HAP measurement. HAP has correlation with age which may be used to reflect the change of vertebral BMD, providing a reference for evaluating BMD according to the linear regression equation.